ⓘ BMW 8 Series (E31)


ⓘ BMW 8 Series (E31)

The BMW E31 is the first generation of the BMW 8 Series. It is a grand tourer built by BMW from 1990 to 1999 powered by either a V8 or V12 engine. While it did supplant the original E24 based 6 Series in 1990, a common misconception is that the 8 Series was developed as a successor. It was actually in an entirely new model class aimed at a different market, with a substantially higher price and performance than the 6 Series.


1. Development

Development of the 8 Series began in July 1981, with both the final design phase reaching completion and production development starting in 1986. The 8 Series debuted at the Frankfurt Motor Show IAA in early September 1989. The 8 Series was designed to move beyond the market of the original 6 Series. The 8 Series had substantially improved performance, as well as a far higher purchase price.

Over 1.5 billion Deutsche Mark was spent on total development 2019 USD nearly $900 million. BMW used CAD tools, still unusual at the time, to design the cars all-new body. Combined with wind tunnel testing, the resulting car had a drag coefficient of C d =0.29, a major improvement from the previous BMW M6/635CSis 0.39.

The 8 Series offered the first V12 engine mated to a 6-speed manual transmission on a road car. It was one of the first vehicles to be fitted with an electronic drive-by-wire throttle. The 8 Series was one of BMWs first cars, together with the Z1, to use a multi-link rear axle.

While CAD modeling allowed the cars unibody to be 3 kg 8 lb lighter than that of its predecessor, the car was significantly heavier when completed due to the large engine and added luxury items - a source of criticism from those who wanted BMW to concentrate on the driving experience. Some of the cars weight may have been due to its pillar-less "hardtop" body style, which lacked a "B" pillar.

Sales of the 8 Series were affected by the global recession of the early 1990s, the Persian Gulf War, and energy price spikes. As a result, plans for the high performance M8 variant were dropped in 1991.

BMW pulled the 8 Series from the North American market in 1997, having sold only 7.232 cars over a seven year period. BMW continued production for Europe until 1999. The worldwide production grand total was 31.062. The base price for an entry-level 8 series in the early 1990s started in the US$70.000 range, which is US$136.987 in 2019.


2.1. Production models 840Ci

The 840Ci was offered with two different engine packages. The first used the 4.0-litre M60B40 V8 engine having a power output of 286 PS 210 kW; 282 hp and was produced from mid-1993 to late 1995. From mid-1995, production phased in the newer 4.4-litre M62B44 V8 engine, which had better fuel economy and more torque, though power output remained unchanged.

The 840Ci was available with a 5-speed automatic transmission, though European cars were given the option of a 6-speed manual transmission. The only external features distinguishing the V8 model from the V12 models were the quad round exhausts, which were square in the V12 models. The 840Ci stayed in production until May 1999.


2.2. Production models 850i

The 850i was the first model of the 8 Series launched in 1990 with the 5.0-litre M70B50 V12 engine having a power output of 300 PS 221 kW; 296 hp. It was available with either a 4-speed automatic or a 6-speed manual gearbox.


2.3. Production models 850Ci

There is some confusion over why and when the 850i became the 850Ci. The change happened around the introduction of the 850CSi and it is believed that BMW decided to include the "C" in the model name that denotes Coupe, just as two-door 3 Series cars alongside the 8 Series read 323Ci, 328Ci and so on. The confusion started when BMW installed the new M73B54 V12 engine in the car. This was not an immediate changeover, and indeed both the M70 and M73-engined cars rolled off the production lines side-by-side for about nine months in 1994, both named 850Ci.

As the displacement of the M73 increased to 5.4-litres and the compression ratio went up, the power output increased to 326 PS 240 kW; 322 hp.


2.4. Production models 850CSi

As a top-of-the-range variant of the 8 Series, the 850CSi took over from the prototype M8 variant. The 850CSi used the same engine as the 850i, which was tuned so significantly that BMW assigned it a new engine code: S70B56. The modifications included Bosch Motronic 1.7 fuel injection, a capacity increase to 5.576 cc 5.6 L and power increase to 280 kW 381 PS; 375 hp at 5.300 rpm and 550 N⋅m 406 lbf⋅ft of torque at 4.000 rpm. Road & Track recorded a 0-60 mph 0-97 km/h time for the 850CSi of 5.9 seconds.

The 850CSis modified suspension included, stiffer springs and dampers that reduced the cars ride height. The recirculating ball steering ratio was dropped 15% over the standard E31 setup. The model also sported staggered throwing star wheels. The front and rear bumpers were reshaped for improved aerodynamic performance. Four round stainless steel exhaust tips replaced the square tips found on other models. The 6-speed manual gearbox was the only transmission option. In Europe, all 850CSis came with four-wheel steering AHK - Aktive Hinterachs-Kinematik, Active rear axle Kinematics, upgraded and ventilated brakes with floating front discs, rear differential oil cooler, engine oil cooler, two-tone interior, sports seats, and reshaped mirrors. In the United States, the cars instead received "BMW Motorsport" writing on the doorhandles.

Production ended in late 1996 because the S70 engine could not be modified to comply with new emission regulations without substantial re-engineering.


2.5. Production models Transmission

The 840Ci 4.0/4.4 L V8 models were equipped with a 5-speed automatic transmission or a 6-speed manual transmission. The 850i/850Ci V12 models each use either a 4-speed automatic transmission or a 6-speed manual transmission, a 5-speed automatic transmission was fitted from mid-1994. The high performance 850CSi model only came with a 6-speed manual transmission.


2.6. Production models Fuel economy

2017 United States Environmental Protection Agency estimates for cars equipped with automatic transmission.


  • Fuel type: Premium
city: 14 miles per US gallon 17 L/100 km; 17 mpg ‑imp highway: 19 miles per US gallon 12 L/100 km; 23 mpg ‑imp combined: 15 miles per US gallon 16 L/100 km; 18 mpg ‑imp


  • Fuel type: Premium
city: 12 miles per US gallon 20 L/100 km; 14 mpg ‑imp highway: 19 miles per US gallon 12 L/100 km; 23 mpg ‑imp combined: 15 miles per US gallon 16 L/100 km; 18 mpg ‑imp

For the 850i, 1991 Sport Model specifically the On-Board computer will typically read 24.6L/100 km when the car is often used under heavy acceleration. These figures could be similar if not slightly less/more for more newer versions of the 850i Sport.


3.1. Prototype models 830i

The 830i was a prototype that did not reach production. As the potential entry-level model, the 830i was to use the 3-liter V8 with 218 PS 160 kW; 215 hp from the 530i and 730i, known internally as the M60B30. Eighteen cars were produced, thirteen of which had an automatic gearbox fitted. The model was dropped in favour of the 840Ci and almost all of the 18 cars were dismantled; one car is in a BMW museum.


3.2. Prototype models 850i Cabrio

The 8 Series had been planned from the start with a convertible version in mind. Although the 850i Cabrio was developed to production readiness, it never went into production. At a relatively late date it was decided that this model was unlikely to recover its development cost. A prototype in red resides in the BMW Museum in Munich.


3.3. Prototype models M8

The M8 was originally envisioned as a Ferrari competitor equipped with a special 558 PS 410 kW; 550 hp version of the S70 engine, which was essentially a bored out version of the M70 with 4-valve per cylinder heads. A common misconception is that this engine powered the McLaren F1. The S70/2 used in the McLaren F1 was not based directly on the prototype 4-valve V12 used in the M8, and was a completely new design.

The project was eventually scrapped because BMW decided that there was no market for a high performance variant of the 8 Series primarily because of the on-going economic recession of the 1990s. The only prototype ever produced one that was reportedly not even safe for normal road usage was locked away by BMW in the companys Giftschrank poison storage. BMW and the M Division had strongly denied that the car was even a possibility since the initial stages of its development. A world exclusive feature in the February 2010 issue of BMW Car Magazine, however, revealed that the M8 prototype still exists in its entirety. The car was unveiled to journalists for the first time on July 2, 2010 at the BMW Museum in Munich. The only public showing of the car happened on August 17, 2012 during The Legends of the Autobahn car show held in Carmel, California. The car was specially shipped from Germany for the appearance.

Although the M8 was never produced, the 850CSi was also tuned by BMWs M division. Aside from sporting an M-tuned engine as identified by the S prefix instead of the M prefix that a non-M tuned engine would bear, the cars VIN identifies the car as being built by BMW Motorsport a WBS prefix instead of BMW AG WBA prefix. Per BMWs own protocol, the 850CSi as marketed was essentially a de-tuned version of the putative M8.


4. Alpina models

B12 5.0

The B12 5.0 was built from 1990 to 1994 based on the BMW E31 850i with an Alpina-modified BMW M70 V12 shared with the E32 B12 5.0 producing 350 PS 257 kW; 345 hp and mated to an automatic transmission.

B12 5.7

The B12 5.7 was available from 1992, based on the BMW 850CSi with the BMW S70B56 V12 engine bored out to 5.7 litres along with a modified intake, crankshaft, camshafts and a stainless steel exhaust system as well as a 6-speed manual gearbox. The modified engine produced 418 PS 307 kW; 412 hp. The carbon-fibre hood had cooling vents and a NACA duct for improved engine cooling. Performance figures included a 0–60 mph 0–97 km/h acceleration time of 5.8 seconds and a top speed of 186 mph 299 km/h.


5. Motorsport

The 8 Series is a very rare car to see in any form of motorsport. One of the most successful examples was built by Wagenstetter Motorsport however, and, until recently, was raced in the Nurburgring VLN endurance championship. It’s based on an 840i, but now has an E39 M5 5.0-litre V8, which has 555 bhp 414 kW; 563 PS and 472 lb⋅ft 640 N⋅m torque, and a six-speed gearbox from the same car.

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